Special gates for PF(n)

For question related to \mathrm{PF}(n) (question 3 in project 1), is there a special gate which preserves the integrity of the bits in the input?
Every time we use a gate, it turns all the inputs into either all 1’s or 0’s based on the truth table, but it doesn’t leave the inputs as they were.

Think about it as an if-then-else block. If the required condition is met, you need to connect the output to the input, else you need to connect the output to zeros. There are special gates which have this functionality which we will cover later on in the course, but you do not need to use them now. Basic gates provided in Logisim’s “Gates” libraries should be enough.